Photoluminescence from GaAs/AlGaAs quantum wires and quantum dots

Abstract

Quantum wires and dots have been fabricated by local interdiffusion of undoped GaAs/AlGaAs quantum well structures. Thermal interdiffusion in induced by a focused laser beam. In periodic arrays of quantum wires the photoluminescence (PL) splitts into several predominant linen which are separated by up to about 8 meV. These PL linen are attributed to the quantum number conserving optical transitionn between 1 dimensional electron and hole levels. Sample inhomogeneities cause broadening of the linen. The transition peaks shift in energy scanning a PL probe with a size of only one micron across the structures. Inhomogeneous line broadening in eliminated by investigation of a single quantum dot. A series of dots with different size show a systematic behaviour of PL blueshift and PL peak splitting. The main peaks in PL and PL excitation (PLE) spectra coincide well in energy and they are separated by up to about 10meV. These peaks can be described by the allowed transitionn between 0D single particles levels within the nearly parabolic potentials caused by interdiffusion. Detailed calculations of excitonic states within the structures result in similar optical spectra. The observation of intense luminescence from excited dot levels indicates a slowing down of the energy relaxation of carriers. Thin is in good agreement with calculated LA phonon emission rates of carries in 0D systems. At low excitation density PL linen from a single quantum dot reveal widths of less than 0.5meV